Navigation maps wrong in Calais

The navigation maps that came with my 2010 Holden VE Series II Calais V wagon appeared to be out-of-date on delivery and I complained to both the dealer and to Holden through the customer satisfaction survey. I asked the dealer how much it would cost to upgrade the maps as I was told that a new release of the maps had recently occurred. I was given a written quote for $500.50, which seemed very costly so I didn't proceed with the update. Are there any cheaper options in updating the Holden navigation maps or do I need to buy a cheaper portable satellite navigation system?